There is disclosed in JP-A-2001-080774 a sheet feeding apparatus having a pickup roller (a delivery roller) that comes into contact with a sheet loaded in a loading section which is provided so as to be vertically movable; and a separation mechanism including a sheet feeding roller (a separation roller) and a separation pad (separation member), both of which are provided downstream of the pickup roller with respect to a transport direction. The sheet feeding apparatus operates in such a way that, as a result of the pickup roller rotating while remaining in contact with the sheet on the loading section, the sheet is delivered to the separation mechanism, and such that the sheet is separated one sheet at a time by means of nipping action performed by the sheet feeding roller and the separation roller and the thus-separated sheet is further transported downstream in the transport direction.
Provided that the pickup roller remains in contact with the sheet at all times, there arises a problem of paper dust or transporting noise being induced by friction between the pickup roller and the sheet or a problem of an increase in transporting load. To solve the problem, the sheet feeding apparatus disclosed in JP-A-2001-080774 activates a solenoid switch at a point in time when the sheet has arrived at a nip position between the sheet feeding roller and the separation roller, thereby separating the pickup roller from the sheet on the loading section.
In an attempt to reduce the size and cost of the apparatus, desire exists for a structure which performs operation for separating the pickup roller by means of gear control while mechanically detecting the position of the pickup roller with minimal use of a custom-designed detection sensor and the like. According to this structure, the loading section is elevated in accordance with the position of the pickup roller. Namely, the loading section is actuated to elevate the position of the pickup roller, which is to come into contact with the sheet on the loading section. When the position of the pickup roller has arrived at a predetermined height, actuation of the loading section is deactivated. When the pickup roller has lowered by a predetermined level as a result of a decrease in the volume of sheet, the loading section is again actuated upwardly.
However, according to this structure, when a housing cassette having the loading section is again set for replenishing the loading section with the sheet, the pickup roller is situated at an initial position spaced away from the sheet, and the loading section is situated at the lowest point. As mentioned previously, the structure is configured to switch elevation of the loading section in accordance with the position of the pickup roller. Accordingly, elevation of the loading section is not commenced until after a gear mechanism has been driven to a certain extent, and hence there arises a problem of occurrence of a failure to feed a sheet (a pickup failure).